c++, coroutines: Make and use a frame access helper.

In the review of earlier patches it was suggested that we might make
use of finish_class_access_expr instead of doing a lookup for the
member and then a build_class_access_expr call.

finish_class_access_expr does a lot more work than we need and ends
up calling build_class_access_expr anyway.  So, instead, this patch
makes a new helper to do the lookup and build and uses that helper
everywhere except instances in the ramp function that we are going
to handle separately.

gcc/cp/ChangeLog:

	* coroutines.cc (coro_build_frame_access_expr): New.
	(transform_await_expr): Use coro_build_frame_access_expr.
	(transform_local_var_uses): Likewise.
	(build_actor_fn): Likewise.
	(build_destroy_fn): Likewise.
	(cp_coroutine_transform::build_ramp_function): Likewise.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index f243fe9adae2b7934aaceac1d00158004d458677..20bda5520c0d014b293323a9208e99abe484c4ea 100644 (file)
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -1670,6 +1670,29 @@ coro_validate_builtin_call (tree call, tsubst_flags_t)
      The complete bodies for the ramp, actor and destroy function are passed
      back to finish_function for folding and gimplification.  */
 
+/* Helper to build a coroutine state frame access expression
+   CORO_FP is a frame pointer
+   MEMBER_ID is an identifier for a frame field
+   PRESERVE_REF is true, the expression returned will have REFERENCE_TYPE if
+   the MEMBER does.
+   COMPLAIN is passed to the underlying functions. */
+
+static tree
+coro_build_frame_access_expr (tree coro_ref, tree member_id, bool preserve_ref,
+                             tsubst_flags_t complain)
+{
+  gcc_checking_assert (INDIRECT_REF_P (coro_ref));
+  tree fr_type = TREE_TYPE (coro_ref);
+  tree mb = lookup_member (fr_type, member_id, /*protect=*/1, /*want_type=*/0,
+                          complain);
+  if (!mb || mb == error_mark_node)
+    return error_mark_node;
+  tree expr
+    = build_class_member_access_expr (coro_ref, mb, NULL_TREE,
+                                     preserve_ref, complain);
+  return expr;
+}
+
 /* Helpers to build EXPR_STMT and void-cast EXPR_STMT, common ops.  */
 
 static tree
@@ -2064,19 +2087,13 @@ transform_await_expr (tree await_expr, await_xform_data *xform)
          We no longer need a [it had diagnostic value, maybe?]
          We need to replace the e_proxy in the awr_call.  */
 
-  tree coro_frame_type = TREE_TYPE (xform->actor_frame);
-
   /* If we have a frame var for the awaitable, get a reference to it.  */
   proxy_replace data;
   if (si->await_field_id)
     {
-      tree as_m
-        = lookup_member (coro_frame_type, si->await_field_id,
-                         /*protect=*/1, /*want_type=*/0, tf_warning_or_error);
-      tree as = build_class_member_access_expr (xform->actor_frame, as_m,
-                                               NULL_TREE, true,
-                                               tf_warning_or_error);
-
+      tree as
+       = coro_build_frame_access_expr (xform->actor_frame, si->await_field_id,
+                                       true, tf_warning_or_error);
       /* Replace references to the instance proxy with the frame entry now
         computed.  */
       data.from = TREE_OPERAND (await_expr, 1);
@@ -2154,13 +2171,10 @@ transform_local_var_uses (tree *stmt, int *do_subtree, void *d)
             known not-used.  */
          if (local_var.field_id == NULL_TREE)
            continue; /* Wasn't used.  */
-
-         tree fld_ref
-           = lookup_member (lvd->coro_frame_type, local_var.field_id,
-                            /*protect=*/1, /*want_type=*/0,
-                            tf_warning_or_error);
-         tree fld_idx = build3 (COMPONENT_REF, TREE_TYPE (lvar),
-                                lvd->actor_frame, fld_ref, NULL_TREE);
+         tree fld_idx
+           = coro_build_frame_access_expr (lvd->actor_frame,
+                                           local_var.field_id, true,
+                                           tf_warning_or_error);
          local_var.field_idx = fld_idx;
          SET_DECL_VALUE_EXPR (lvar, fld_idx);
          DECL_HAS_VALUE_EXPR_P (lvar) = true;
@@ -2250,12 +2264,8 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
   local_vars_transform xform_vars_data
     = {actor, actor_frame, coro_frame_type, loc, local_var_uses};
   cp_walk_tree (&fnbody, transform_local_var_uses, &xform_vars_data, NULL);
-
-  tree rat_field = lookup_member (coro_frame_type, coro_resume_index_id,
-                                 1, 0, tf_warning_or_error);
-  tree rat = build3 (COMPONENT_REF, short_unsigned_type_node, actor_frame,
-                    rat_field, NULL_TREE);
-
+  tree rat = coro_build_frame_access_expr (actor_frame, coro_resume_index_id,
+                                          false, tf_warning_or_error);
   tree ret_label
     = create_named_label_with_ctx (loc, "actor.suspend.ret", actor);
 
@@ -2345,10 +2355,8 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
   add_stmt (r);
 
   /* actor's coroutine 'self handle'.  */
-  tree ash_m = lookup_member (coro_frame_type, coro_self_handle_id, 1,
-                             0, tf_warning_or_error);
-  tree ash = build_class_member_access_expr (actor_frame, ash_m, NULL_TREE,
-                                            false, tf_warning_or_error);
+  tree ash = coro_build_frame_access_expr (actor_frame, coro_self_handle_id,
+                                          false, tf_warning_or_error);
   /* So construct the self-handle from the frame address.  */
   tree hfa_m = get_coroutine_from_address (orig);
   /* Should have been set earlier by coro_promise_type_found_p.  */
@@ -2391,11 +2399,9 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
 
   /* Here deallocate the frame (if we allocated it), which we will have at
      present.  */
-  tree fnf_m
-    = lookup_member (coro_frame_type, coro_frame_needs_free_id, 1,
-                    0, tf_warning_or_error);
-  tree fnf2_x = build_class_member_access_expr (actor_frame, fnf_m, NULL_TREE,
-                                               false, tf_warning_or_error);
+  tree fnf2_x
+   = coro_build_frame_access_expr (actor_frame, coro_frame_needs_free_id,
+                                  false, tf_warning_or_error);
 
   tree need_free_if = begin_if_stmt ();
   fnf2_x = build1 (CONVERT_EXPR, integer_type_node, fnf2_x);
@@ -2403,11 +2409,9 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
   finish_if_stmt_cond (cmp, need_free_if);
   while (!param_dtor_list->is_empty ())
     {
-      tree pid = param_dtor_list->pop ();
-      tree m = lookup_member (coro_frame_type, pid, 1, 0, tf_warning_or_error);
-      gcc_checking_assert (m);
-      tree a = build_class_member_access_expr (actor_frame, m, NULL_TREE,
-                                               false, tf_warning_or_error);
+      tree parm_id = param_dtor_list->pop ();
+      tree a = coro_build_frame_access_expr (actor_frame, parm_id, false,
+                                            tf_warning_or_error);
       if (tree dtor = cxx_maybe_build_cleanup (a, tf_warning_or_error))
        add_stmt (dtor);
     }
@@ -2504,11 +2508,8 @@ build_destroy_fn (location_t loc, tree coro_frame_type, tree destroy,
     = cp_build_indirect_ref (loc, destr_fp, RO_UNARY_STAR,
                             tf_warning_or_error);
 
-  tree rat_field = lookup_member (coro_frame_type, coro_resume_index_id,
-                                 1, 0, tf_warning_or_error);
-  tree rat
-    = build_class_member_access_expr (destr_frame, rat_field, NULL_TREE,
-                                     /*reference*/false, tf_warning_or_error);
+  tree rat = coro_build_frame_access_expr (destr_frame, coro_resume_index_id,
+                                          false, tf_warning_or_error);
 
   /* _resume_at |= 1 */
   tree dstr_idx
@@ -4836,13 +4837,9 @@ cp_coroutine_transform::build_ramp_function ()
        {
          bool existed;
          param_info &parm = param_uses.get_or_insert (arg, &existed);
-
-         tree fld_ref = lookup_member (frame_type, parm.field_id,
-                                       /*protect=*/1, /*want_type=*/0,
-                                       tf_warning_or_error);
          tree fld_idx
-           = build_class_member_access_expr (deref_fp, fld_ref, NULL_TREE,
-                                             false, tf_warning_or_error);
+           = coro_build_frame_access_expr (deref_fp, parm.field_id,
+                                           false, tf_warning_or_error);
 
          /* Add this to the promise CTOR arguments list, accounting for
             refs and special handling for method this ptr.  */